The seatbelt pretensioner is known as one of the safety systems to protect a vehicle occupant from the shock in a car collision. The seatbelt pretensioner is structured to operate a cylinder by a large amount of high-temperature and high-pressure gas generated by the gas generator. The gas generator, which is used to operate the cylinder, not an airbag, is structured to generate a relatively small amount of gas and to inject the high-temperature and high-pressure gas directly to the cylinder without any intermediary of filter or coolant. Usually, this gas generator includes a squib containing an ignition charge to be ignited by an electric current through the squib, a first cup case containing gas generant, and a holder to fixedly hold the squib and the first cup case.
An example of a conventional gas generator used for the seatbelt pretensioner is shown in FIG. 3. The gas generator 108 of FIG. 3 comprises gas generant 106 that generates a large amount of gas by the ignition, a squib 104 containing an ignition charge that is ignited by the passage of electric current through the squib, a first cup case 102 containing the gas generant, a holder 101 to hold the squib 104 and the first cup case 102 concentrically and seal the gas generant 106 and the squib 104 shown in FIG. 5 in an inner space between the holder 101 and the first cup case 102, an O-ring 105 disposed in a gap between the squib 104 and the holder 101 to prevent moisture from entraining from the gap therebetween, and a shorting clip 107 to keep two electrode pins 11, 12 standing from the squib 104 in a shorted state. Also, a sealant, not shown, is applied to the gap between the first cup case 102 and the holder 101 to prevent moisture from entraining the gap therebetween.
The squib 104 comprises a second cup case E containing an ignition charge D, header B inserted and fitted in the second cup case E to seal the ignition charge D in an interior of the second cup case E, and two electrode pins 11, 12 of metal rods extending through the closing plug B, as shown in FIG. 5. The electrode pins 11, 12 project in the interior of the second cup case E and are electrically connected to each other at their front ends through an electric bridge-circuit wire F. The electric bridge-circuit wire F is covered with fuse head C contacting with the ignition charge D. The closing plug B is formed of a resin in order to provide electrical insulation between the respective electrode pins 11, 12 except the portions thereof corresponding to the electric bridge-circuit wire.
The squib 104 is held by the holder 101, with its tapered portion 109 contacting with a tapered portion 110 of the holder 101, as shown in FIG. 3. Also, the bottom thereof 111 of the closing plug B of the squib 104 is exposed to the outside (See FIG. 4(a)). Incidentally, the closing plug B formed of resin may be softened by the heat resulting from the ignition in the high-temperature state. Due to this, there is a possibility that the electrode pins 11, 12 in the closing plug B may be dropped out together with the closing plug B when softened and reduced in retention.
It is an object of the present invention to provide a gas generator with enhanced safety that can prevent a drop-out of the electrode pins standing from the squib of the gas generator when ignited in a high temperature state.